Magnetic sensor module

ABSTRACT

In a magnetic sensor module, using die-bond resin as a joining material, a Z-axis magnetic sensor is mounted onto a substrate having a wire formed on its principal surface. The Z-axis magnetic sensor having electrode pads formed on its bottom surface is tilted by 90 degrees and mounted onto the substrate. Therefore, the electrode pads are positioned at a side surface thereof. A joining material accommodation area which the die-bond resin can fill is provided at the surface of the Z-axis magnetic sensor opposing the principal surface of the substrate. This joining material accommodation area has a grooved structure. At the surface of the Z-axis magnetic sensor opposing the principal surface of the substrate, the grooved structure is provided at an end portion near the wire formed on the substrate.

This application is a Continuation of International Application No.PCT/JP2008/066292 filed on Sep. 10, 2008, which claims benefit of theJapanese Patent Application No. 2007-233820 filed on Sep. 10, 2007, bothof which are hereby incorporated by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a magnetic sensor module used in, forexample, an electronic compass.

2. Discussion of the Related Art

An electronic compass including a magnetic sensor that detectsgeomagnetism detects the geomagnetism by, for example, an X-axismagnetic sensor, a Y-axis magnetic sensor, and a Z-axis magnetic sensor.In such an electronic compass, an IC and a magnetic sensor are mountedon a substrate, and the IC and the magnetic sensor are electricallyconnected to each other. The magnetic sensor is ordinarily designed soas to have a sensitivity axis in only one direction, and has asubstantially rectangular parallelepiped shape. Therefore, in order tomount three magnetic sensors on the same substrate, it is necessary totilt one magnetic sensor or two magnetic sensors by 90 degrees and toset its sensitivity axis or their sensitivity axes orthogonally to theother magnetic sensor or magnetic sensors.

If a magnetic sensor is tilted by 90 degrees in this way, as shown inFIG. 4A, electrode pads 32 that are ordinarily formed at the bottomsurface of a magnetic sensor 31 so as to be mounted to a surface of asubstrate are positioned at a side surface thereof. In this case, acorner bump bonding method that electrically connects the electrodepads, which are positioned at the side surface of the component, andwires, which are formed on the surface of the substrate, to each otheris used (Japanese Unexamined Patent Application Publication No.2000-155922).

In manufacturing the magnetic sensor 31, after forming many elements ona wafer, the elements are divided into separate elements by dicing. Inthis case, as shown in FIG. 4B, it is necessary to provide a distance Xfrom a peripheral edge of the magnetic sensor 31 to the electrode pads32 so that chipping Y occurring during the dicing does not influence theelectrode pads 32. If the distance X from the peripheral edge of themagnetic sensor 31 to the electrode pads 32 is provided, as shown inFIG. 5, the distance between a wire 34, formed on a substrate 33, andthe electrode pads 32, provided at the magnetic sensor 31, is increased.As a result, it is necessary to increase the outside diameter of bumps36 that electrically connect the wire 34 and the electrode pads 32 toeach other. If the outside diameter of the bumps 36 is increased, it isnecessary to increase the pitch between the electrode pads 32 forpreventing short-circuiting between the bumps 36. This results in theproblem that a magnetic sensor module cannot be reduced in size.

BRIEF SUMMARY

The present invention is carried out in view of the aforementionedpoints, and provides a magnetic sensor module which can be reduced insize with a magnetic sensor and a substrate being electrically connectedto each other by corner bump bonding.

According to the present invention, there is provided a magnetic sensormodule including a substrate, a magnetic sensor, and a second joiningmaterial. The substrate has a wire on a principal surface thereof. Themagnetic sensor has an electrode pad formed on one surface thereof, ismounted on the principal surface of the substrate using a first joiningmaterial so that another surface thereof orthogonal to the one surfaceopposes the principal surface of the substrate, and has a joiningmaterial accommodation area that is situated between the electrode padand the another surface and that is capable of being filled with thefirst joining material. The second joining material electricallyconnects the wire and the electrode pad to each other.

According to this structure, the electrode pads and the wire can bebrought close to each other. Therefore, it is possible to reduce thesize of the second joining material, and to reduce the pitch between theelectrode pads. As a result, it is possible to reduce the size of themagnetic sensor and the magnetic sensor module.

In the magnetic sensor module according to the present invention, thejoining material accommodation area may be formed so as to have agrooved structure provided at an end portion near the wire.

In the magnetic sensor module according to the present invention, themagnetic sensor may have a sensitivity axis in a direction substantiallyorthogonal to the principal surface.

In the magnetic sensor module according to the present invention, athickness of the wire may be greater than a length equal to the sum of adistance from the electrode pad to the joining material accommodationarea and a thickness of the first joining material.

The magnetic sensor module according to the present invention includes asubstrate, a magnetic sensor, and a second joining material. Thesubstrate has a wire on a principal surface thereof. The magnetic sensorhas an electrode pad formed on one surface thereof, is mounted on theprincipal surface of the substrate using a first joining material sothat another surface thereof orthogonal to the one surface opposes theprincipal surface of the substrate, and has a joining materialaccommodation area that is situated between the electrode pad and theanother surface and that is capable of being filled with the firstjoining material. The second joining material electrically connects thewire and the electrode pad to each other. Therefore, it is possible toreduce the size of the magnetic sensor module with the magnetic sensorand the substrate being electrically connected to each other by cornerbump bonding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a magnetic sensor package including amagnetic sensor module according to an embodiment of the presentinvention;

FIG. 2 shows a state in which a magnetic sensor of the magnetic sensormodule shown in FIG. 1 is mounted;

FIG. 3 illustrates the process of producing the magnetic sensor of themagnetic sensor module shown in FIG. 1;

FIGS. 4A and 4B illustrate a related magnetic sensor; and

FIG. 5 shows a state in which a magnetic sensor of the related magneticsensor module is mounted.

DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERREDEMBODIMENTS

An embodiment of the present invention will hereunder be described indetail with reference to the attached drawings.

FIG. 1 is a perspective view of a package including a magnetic sensormodule according to an embodiment of the present invention. The magneticsensor module shown in FIG. 1 includes an interposer, which is asubstrate 11. The substrate 11 has a pair of opposing principalsurfaces, with an IC 12 being mounted on one of the principal surfaces.An X-axis magnetic sensor 13 a, a Y-axis magnetic sensor 13 b, and aZ-axis magnetic sensor 13 c are mounted to the same principal surface.Although, in the embodiment, the case in which three magnetic sensorsare mounted to the substrate 11 is described, in the present invention,at least one magnetic sensor may be mounted onto the substrate 11.

Electrode pads are formed on the substrate 11, the IC 12, and themagnetic sensors 13 a to 13 c. The substrate 11 and the IC 12 and the IC12 and the magnetic sensors 13 a to 13 c are wire-bonded by wires 14. Bythis, the substrate 11, the IC 12, and the magnetic sensors 13 a to 13 care electrically connected to each other. One of the principal surfacesides of the substrate 11 is packaged by a package material 15.

FIG. 2 shows a form in which the Z-axis magnetic sensor of the magneticsensor module shown in FIG. 1 is mounted. In the magnetic sensor module,using die-bond resin 22 as a joining material, the Z-axis magneticsensor 13 c is mounted onto the substrate 11 having a wire 21 formed onits principal surface. The Z-axis magnetic sensor 13 c having electrodepads 23 formed on its bottom surface is tilted by 90 degrees and mountedonto the substrate 11. Therefore, the electrode pads 23 are positionedat a side surface thereof. Consequently, the electrode pads 23 extendsubstantially orthogonal to the principal surface of the substrate 11.The Z-axis magnetic sensor 13 c is such that a direction along theprincipal surface at which the electrode pads 23 are formed correspondsto a sensitivity axis direction. Therefore, by tilting the sensor 13 cby 90 degrees and mounting it to the substrate 11, the sensitivity axisdirection becomes the direction substantially orthogonal to theprincipal surface of the substrate 11. Accordingly, the Z-axis magneticsensor 13 has the electrode pads 23 formed on one surface thereof, ismounted to the principal surface of the substrate 11 using the die-bondresin 22 so that another surface that is orthogonal to the one surfaceof the Z-axis magnetic sensor 13 opposes the principal surface of thesubstrate 11, and has a joining material accommodation area (describedlater) in which the die-bond resin can fill a portion between theelectrode pads 23 and the another surface.

The joining material accommodation area in which the die-bond resin canbe filled is provided at the surface of the Z-axis magnetic sensor 13 copposing the principal surface of the substrate 11. This joiningmaterial accommodation area has a grooved structure 24. At the surfaceof the Z-axis magnetic sensor 13 c opposing the principal surface of thesubstrate 11, the grooved structure 24 is provided at an end portionnear the wire 21 formed on the substrate 11. It is desirable that thedepth of a groove of the grooved structure (the size in a directionorthogonal to the principal surface of the substrate 11 in FIG. 2) beset so as to be at least smaller than a thickness t of the wire 21. Bysetting the depth thus, it is possible to prevent the die-bond resin 22from flowing to a bump formation portion of the wire 21 when mountingthe Z-axis magnetic sensor 13 c onto the substrate 11 by the die-bondresin 22. From such a viewpoint, it is desirable that the thickness t ofthe wire 21 be greater than a length equal to the sum of a distance afrom the electrode pads 23 to an end portion of the grooved structure 24(that is, the distance a to an outer edge of the Z-axis magnetic sensor13 c at the joining material accommodation area) and a thickness of thedie-bond resin 22 (that is, a thickness b between the substrate 11 andan area other than the joining material accommodation area of the Z-axismagnetic sensor 13 c).

It is desirable that the distance from a wire-21-side end portion of thegrooved structure 24 to the wire 21 be greater than the thickness of theelectrode pads 23. By such a setting, when the Z-axis magnetic sensor 13c is mounted onto the substrate 11 by the die-bond resin 22, it ispossible to prevent the flow of the die-bond resin 22 to the bumpformation portion of the wire 21.

The wire 21 and the electrode pads 23 are electrically connected to eachother by a bump (such as an Au bump) 25 serving as a joining material.By this, the Z-axis magnetic sensor 13 c is mounted onto the substrate11 by corner bump bonding.

In the magnetic sensor module having the above-described structure, theelectrode pads 23 and the wire 21 can be brought close to each other.Therefore, it is possible to reduce the size of the bump 25, and toreduce the pitch between the electrode pads 23. As a result, it ispossible to reduce the size of the magnetic sensor and the magneticsensor module.

In addition, in this structure, even if the die-bond resin 22 is used,since the grooved structure 24, serving as the joining materialaccommodation area, is provided, the die-bond resin 22 that flows duringmounting fills the grooved structure 24. This makes it possible toprevent the die-bond resin 22 from flowing out to the wire 21 and theelectrode pads 23. As a result, it is possible to more reliablyelectrically connect the bump 25, the wire 21, and the electrode pads 23to each other, and to increase allowable variations in the requiredapplication amount of the die-bond resin 22.

Further, in this structure, since the die-bond resin 22 fills thegrooved structure 24, the difference between the amount of die-bondresin 22 at an area of the Z-axis magnetic sensor 13 c opposite to thewire 21 and the amount of die-bond resin 22 that fills the groovedstructure 24 can be reduced. Therefore, both sides (the wire side andthe side opposite to the wire) of the Z-axis magnetic sensor 13 c areheld by substantially equal forces, so that it is possible to reducetilting and positional displacement of the Z-axis magnetic sensor 13 cmounted onto the substrate 11.

When the grooved structure 24 is formed in the magnetic sensor havingthe above-described structure, as shown in FIG. 3, first, half dicing iscarried out using a dicing saw that has an edge having a relativelylarge width to form a groove 27 in a wafer 26 having elements formedthereon. Thereafter, dicing is carried out using a dicing saw that hasan edge having a relatively small width to form a chip. By carrying outsuch a step cutting operation, the grooved structure 24 can be providedin the magnetic sensor. In addition, if, first, dicing is carried outunder a condition in which chipping does not easily occur when the halfdicing is carried out, and, then, dicing at a high speed is carried outusing the dicing saw having a small width, chipping does not easilyoccur near the electrode pads, and dicing providing excellentproductivity can be carried out. This makes it possible to set thepositions of the electrode pads near an end portion of the magneticsensor, thereby making it possible to further reduce the size of thebump 25.

Next, an example that was achieved for clarifying the advantages of thepresent invention will be described.

As a module substrate (interposer), a glass epoxy substrate having awire that is 20 μm thick formed on one of the principal surfaces wasprovided. In addition, a magnetic sensor having electrode pads and agrooved structure such as that shown in FIG. 2 was provided. Here, thepitch between the electrode pads of the magnetic sensor was 90 μm, andthe size of the grooved structure was 2 μm×30 μm. Further, the distancea to an outer edge of the magnetic sensor at the grooved structure was 7μm.

Such a magnetic sensor was disposed so that the grooved structure facedthe module substrate, and, using die-bond resin, the magnetic sensor wasmounted onto the module substrate. At this time, the thickness b of thedie-bond resin was 3 μm. That is, the thickness (20 μm) of the wire wasgreater than the length equal to the sum of the distance a (7 μm) fromthe electrode pads to an end portion of the grooved structure and thethickness b (3 μm) of the die-bond resin. The electrode pads and thewire of the magnetic sensor mounted in this way were subjected to cornerbump bonding at an Au bump having a bump diameter of 50 μm, to produce amagnetic sensor module.

In the magnetic sensor module produced in this way, since the groovedstructure was provided, the die-bond resin filled the grooved structure,and did not flow out to the wire. In addition, it was possible to carryout the corner bump bonding without short-circuiting at the Au bump.Accordingly, since it was possible to reduce the distance between thewire and the electrode pads, it was possible to reduce the bump diameterto 50 μm. Therefore, it was possible for the pitch between the electrodepads to be 90 μm. Further, since the die-bond resin holds both sides ofthe magnetic sensor by substantially equal forces, the chip angle of themagnetic sensor mounted on the module substrate was a predeterminedangle (that is, the sensitivity axis was oriented in a predetermineddirection).

The present invention is not limited to the above-described practicalforms, and can be variously modified and carried out. Within the scopeof the present invention, for example, the number, the disposition, andthe materials of the members can be changed as appropriate to carry outthe present invention. In addition, within the scope of the presentinvention, the present invention can be modified as appropriate to carryout the present invention.

1. A magnetic sensor module comprising: a substrate having a wire on aprincipal surface thereof; a magnetic sensor having an electrode padformed on one surface thereof, the magnetic sensor being mounted on theprincipal surface of the substrate using a first joining material sothat another surface thereof orthogonal to the one surface opposes theprincipal surface of the substrate, the magnetic sensor having a joiningmaterial accommodation area that is situated between the electrode padand the another surface and that is capable of being filled with thefirst joining material; and and a second joining material electricallyconnecting the wire and the electrode pad to each other.
 2. The magneticsensor module according to claim 1, wherein the joining materialaccommodation area has a grooved structure provided at an end portionnear the wire.
 3. The magnetic sensor module according to claim 1,wherein the magnetic sensor has a sensitivity axis in a directionsubstantially orthogonal to the principal surface.
 4. The magneticsensor module according to claim 1, wherein a thickness of the wire isgreater than a length equal to the sum of a distance from the electrodepad to the joining material accommodation area and a thickness of thefirst joining material.